As an image display device which is thin and has a big screen, a plasma display panel (hereinafter called as PDP) in which light is produced by electric discharge between a front glass plate and a rear glass plate, is in widespread use. In the PDP, to shield electromagnetic waves generated by the electric discharge, an electromagnetic shielding is provided. As the electromagnetic shieldings, there are a thin metal film formed on the front glass plate and an electromagnetic shielding film provided at a front side of the front glass plate. Recently, the electromagnetic shielding film having high shielding performance and high optical transparency is mainly used. The electromagnetic shielding film is a transparent film on which a metal mesh (thin metal lines arranged in a mesh shape) is formed.
Conventionally, the electromagnetic shielding film is formed by pasting a transparent film and a metal foil, and applying a photoetching process to make the metal foil into the mesh shape. However, the applicant has developed an electromagnetic shielding film formed by silver halide photography technique, in which minute meshes of silver halide are formed on a transparent film. In this electromagnetic shielding film, any shape of mesh pattern can be made and size and definition can be appropriately matched to specifications of the panel. In addition, since the pasting of the transparent film and the metal foil, which is complicated and has poor yield, is not required, the cost is reduced and stable supply is realized.
To form the electromagnetic shielding film, a mesh pattern is exposed on a silver salt photosensitive material coated on the transparent film by radiation of light through a mask, and then a mesh of silver salt appears on the transparent film by development. Since a pitch and line width of the mesh largely affect image quality of the PDP, a pattern exposure with high accuracy is required.
Conventionally, in a color filter for display devices, a light shielding pattern and color patterns are formed. To form these patterns, pattern exposure method and apparatus, in which light is radiated on a work having a photosensitive layer through a mask to expose patterns on the work, are used. There are some approaches to apply this method to an exposure process for the electromagnetic shielding film. For example, JP-A-9-274323 discloses a pattern exposure method in which light is radiated though a mask to form a pattern on a belt-like work which is continuously conveyed. In addition, JP-A-10-171125 discloses a proximity exposure apparatus in which positioning, gap setting and proximity exposure are repeated to form a pattern on a belt-like work which is intermittently conveyed.
However, in the pattern exposure method of JP-A-9-274323, since only a stripe pattern parallel to a conveying direction of the belt-like work can be exposed, periodic patterns having various shapes along the conveying direction, such as a mesh pattern suitable for the electromagnetic shielding film, cannot be exposed.
In the proximity exposure apparatus of JP-A-10-171125, although any patterns including periodic patterns can be exposed, a processing capacity per unit time (throughput) is low because total time of the positioning, the gap setting and the exposure during the intermittent conveyance becomes large.
An object of the present invention is to provide a pattern exposure method which can form periodic patterns of various shapes arranged in a work conveying direction in high throughput, and a simple and low cost pattern exposure apparatus for forming the patterns.